The present invention relates to printers, and more particularly, to supplying power and signal to print carriages.
Some plotters and printers (collectively, xe2x80x9cprintersxe2x80x9d) such as those used with home or business personal computers (PC""s) print each swath of text or graphics by moving pens or printheads (collectively, xe2x80x9cpensxe2x80x9d) relative to paper moving through the printer. Typically, the pens are mounted on a motorized printer carriage that moves back and forth over the paper.
Typically, a flexible cable connects the carriage to a printer control system of the printer. In that configuration, the flexible cable delivers power, provides ground, and delivers data and control signals to the carriage, ultimately controlling the pens.
Such system is illustrated in FIG. 1. In FIG. 1, a printer 10 includes a printer carriage 12 connected to a printer control system 13 (hidden under a receiving station 14) via a flexible cable 18. The printer control system 13 is illustrated in FIG. 2 and can include power supply portion and a data and control portion. In the illustrated sample, the carriage 12 includes four pens 16. Further, in the illustrated sample, the flexible cable 18 is a xe2x80x9cribbonxe2x80x9d cable including a plurality of flexible wires.
The flexible cable 18, tethering the print carriage 12 to the printer control system 13, degrades quality of the printer due to its mechanical nature. This is better illustrated using FIG. 2. FIG. 2 is a simplified schematic representation of the printer 10 of FIG. 1. Ideally, the pens 16, thus the carriage 12, of the printer 10 contact the plane 22 of the paper 24 at a normal angle to the plane 22 of the paper 24. Any angular rotation or torque of the carriage 12 relative to the plane 22 of the paper 24 decreases print quality. Such angular torque of the carriage 12 are caused by varying torsional forces (illustrated as a directed arc 26) exerted by the flexible cable 18 as it is stretched, compressed, or otherwise moved during the movement of the carriage 12. In the illustrated printer 10, the carriage 12 moves by sliding on a sliding bar 28 in the horizontal directions indicated by a directed line 30. The degree of torsional force 26 depends on various factors including mass, length, and stiffness of the flexible cable 18, current slackness and compression of the flexible cable 18, and speed of the movement of the carriage 12.
Further, the flexible cable 18 presents hurdles to improvements in print quality and speed. For example, print quality and speed can be improved by increasing the number of pens in the carriage. However, the increase in the number of pens requires heavier wire in the flexible cable 18 to carry more power. Moreover, the increase in the number of pens requires additional data lines in the flexible cable 18 to control the additional pens. The increase in the mass of the flexible cable increases angular torque 26 of the carriage 12 thereby reducing print quality. Moreover, the increase in the mass of the flexible cable 18 decreases the speed in which the carriage 12 can be moved thereby negating the gains in the print speed due to the additional pens.
Accordingly, there is a need for an improved apparatus to deliver power, data, and control to the printer carriage to overcome these shortcomings.
These needs are met by the present invention. According to one aspect of the present invention, a printer has a power bus for delivery of power to a print carriage and a first charge pickup system for transfer of power from the power bus to the print carriage.
According to another aspect of the present invention, a printer comprising includes a power bus and a ground return bus. A first charge pickup system transfers power from the power bus to a print carriage. A second charge pickup system provides a ground return path to the print carriage. The first charge pickup system has a first conductor facilitating the transfer of power and a spring for maintaining contact between the power bus and the print carriage. The second charge pickup system has a second conductor connecting the print carriage to the ground return bus.
Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in combination with the accompanying drawings, illustrating by way of example the principles of the invention.